Biology Reference
In-Depth Information
6
The duplicity theory of Polyak
After a comprehensive review of the anatomical and histological
research on the organs of vision from the classical antiquity to his
own time, Polyak (1941) concluded that this research had played a
relatively insignificant role in forming hypotheses and theories of the
function
of the visual system. A major reason was that the retina of
humans and other primates had never been examined in any detail by
analytical histological methods such as those of Golgi and Ehrlich.
These methods, although very time consuming, were preferable,
since they permitted the staining of only a few nerve cells at a time
from the bewildering mass of tissues. Indeed, in successfully treated
preparations, the individual neurons could be stained completely,
revealing the whole nerve cell with all its extensions and branches
extending as far as the finest terminals. Furthermore, he held that a
disclosure of the structural details of the retina of primates would
make possible interpretations related to the many psychophysical
functions already established in humans.
Polyak, therefore, completed a very impressive histological
investigation on the retina of macaques and chimpanzees, using
the Golgi method. He also occasionally used retinas from humans.
His comprehensive and seminal research work (summarized in
1941; second impression, 1948) has long been recognized as a classic
contribution to our knowledge of the retinal structure and function
in primates.
His results confirmed two of the basic findings of Schultze
(
1866
): (1) the retina of primates contained two morphologically clearly
differentiated varieties of photoreceptors, the rods and cones, and (2) the
structure of cones did not differ essentially within any of the retinal
regions. They all appeared to belong to the same variety, possessing
